As latin and catholic countries, and as countries that border the mediterranean, both countries have obviously common points. That said one should not over-estimate and think that they are the same on all points.
On the points you noticed, "culturally catholic, passion for living, love food, family oriented..." These actually are not specific of Spain/Italian relation but could apply to most latin countries as a whole; Italy, France, Spain, Portugal, not onlt Spain and Italy. Actually concerning passion for food and living, it's actually much more a french/Italian thing that a Spanish one.
For being "partying" it is mainly a Spanish thing, and less Italian. "family-oriented" is something traditional in most mediterranean and/or catholic countries; it concerns especially the south of both countries than many other areas; not that much in northern Italy.
On the question of "sunny mediterranean climate"; while true for many areas; it is a over-simplification. Many regions in both countries have not really mediterranean climates, especially in Spain. For exemple, Spain borders as much the Atlantic as it does with the mediterranean. Climate in northern Spain is mild, but not mediterranean at all: it has wet and relatively cool summers, with completly different landscapes:
Most of the inside of Spain, (Castillan plateaus); has harsher climates, especially the region of Castilla-y-Leon, with winters quite different to the mild mediterranean regions.
In the Po plain in northern Italy the climate is not mediterranean either. these regions are the ecomic heart of Italy and the most densily populated area of the country, but quite far from the traditional cliché of the country that is usually more based on the peninsula and its mediterranean ambiance. This part of Italy has cold winters and many days of mist, and different kind of foods than peninsular Italy.
The climate is often though to be very similar between both countries because they are often though to be at the same latitudes. Actually, Italy is quite much further north than Spain: the northern half of Italy is in line with the southern half of France; when the southern half of Italy only is in line with Spain. Everything that in Italy is further north than Rome is more in line with France than with Spain (and touch it, when Spain is a few hundred of kilometers farther)
Imageshack - franceitalyspain.jpg
Actually the European regions outside of Italy that has more common points with the Italian stereotypes in terms of climate, landscapes, food or architecture is probably Provence, Nice and Corsica in France more than any part of Spain. This is actually logical when we see that this region is just west of Tuscany, the "quintessential Italian region"...
http://ecogitedebivosque.wifeo.com/images/100_4370.jpg (broken link)
Inversely, in southern France, as we cross the Rhone valley in direction to the west, we enter in areas that have many cultural aspects that exist in Spain, Portugal and France but doesn't exist in Italy.
Especially the different kinds of Bullfighting traditions, that are emblematic of Spain, are also a important traditional aspect in many parts of southern French regions that are situated west of the Rhone. The Bullfight culture and the Ferias of Nimes, Arles, Dax and many other parts of southern France make them very similar to the Spanish culture. In Italy this is a very foreign thing. Even the vernacular architecture in those areas is more like what could be found in Spain (less colorfull, more "serious", "proud" and "simple", or even "military" than the more "italian-like" urban ambiances of Provence, Nice or Corsica, much more "messy" and colorful.
I tend to think that is we speak generally of the typically, stereotipically "spirit" of Spanish and Italian cultures, (without taking in account the huge regional diversities), diverge hugely mainly on this aspect: Italian culture is associated with warmness, color, messy things, sympathetic but "not-very-serious" attitudes, theater-like acting in everyday life, chaos, etc... (although these things are not very true in the northermost regions, this is a stereotype)
when Spain is almost the reverse on this: contrasted, harsher, tragic, dramatic, serious, proud, ordely.
This Italian stereotype is mostly base on peninsular Italy, while this Spanish stereotype is based more on the Castilla plateaus regions, where the climate and landscape is harsher.
This is reflected in the arts very strongly (painting, architecture or music). Italian art is harmony, calm, sweet proportions, when Spanish one is more based on proudness, tragic, bloodly.
Let's see some exemples:
Asturias - Isaac Albeniz - YouTube
Concerto d'Aranjuez - John Williams - Vidéo Dailymotion
This could hardly being produced by Italian artists
Concerning the languages, Spanish and Italian are both latin languages (or "romance"). As such they have many similarities, but not really more together than they would have with other latin languages.
Actually Spanish is much more similar with Portuguese than with any other latin language. Culturally speaking, as a whole Spain is also much closer to Portugal than to Italy. Spain has also I I said above, as much (if not more) in common with the neighboring regions of France than with Italy.
Italian and Spanish are often said or thought to be the most similar of Romance languages because of their phonology that is to the ear more similar that it can be with Portuguese or with French. But still the accent and intonation are very different (Italian being once again more towards sweetness and melody, while Spanish has that deeply tragic thing in its rythms and sounds)
On the pure linguistic point of view (vocabulary and Grammar), Italian is actually closer to French than it is to Spanish, contrary to the common belief. Foreigner might think French and Italian are distant because they sound quite differently (especially because standard french is the northern version of it, actually spoken by southern accents french is as much melodic as Italian is). French and Italian share 89% of related vocabulary, while Italian and Spanish share 75%.
But concerning languages we should not forget that in the three countries there is (or used to be until a few decades), regional languages that are actually often somehow in-between the three. Catalan, which is spoken in almost all the mediterranean coast of Spain is actually on many points as much close to French and Italian, that it is to Castillan Spanish. The same way, in the south of France, the Occitan dialects that used to be spoken until the last centuries were very similar to Catalan. In Northern Italy there used to be languages that were usually considered Closer to French than to Tuscan (Standard Italian).
In my opinion (I'm a southern French that travelled extensively in France, Spain and Italy), all these three countries (+Portugal), share the same cultural group in Europe; which is usually called "latin" refering to the roots of the languages and the cultural herency of the former Roman empire, and catholicism. the regions of these countries present a continuum of landscapes and local cultures without som much harsh transition. In that way, southern France is in many ways, the intermediary zone, or "buffer zone" between Italian, Northern French and Spanish cultures. Catalan culture in Spain is an intermediary step between southern French and Castillan culture, etc...
French culture and language is often thought by many foreign people to be very different from Spanish/Italian ones. I don't think that is the case, either on linguistic facts (see above) or cultural ones. It depends actually on what part of the countries on which we base the stereotypes.
It seems that the common stereotype from Spain is based on Andalucian culture (flamenco, images of white villages, gypsies, etc), that Italian clichés are more based on southern Italy (south or Rome), when French images seem to be focused exclusively on Paris and its surroundings in the Northern half of France.
That ways it is not surprinsing that the idea that France and Italy could be culturally as much close that Spanish and Italy can be is usually not accepted. But when you know the languages and the different regions in the countries you realize that they can be very similar on many ways. Especially if we compare the northern half of Italy with the southern half of France. The regions around Lyon are culturally similar to piemonte or Lombardy. Provence is culturally very similar to Tuscany, etc.