The thing is that my father has a blog in spanish and I just noticed that although he has no idea of link development and SEO he has a nice Page Rank of 4 (which is pretty good). So I was thinking of linking from that blog to mine in his blog roll, but will this affect negativley his page rank/rankings? and will this be of any help to my NEW blog?
Well, unless your blog has malware or illegal stuff, I don't think so. Of course. Especially if your blog's topic is similar or related to your father's.
There's no harm at all in linking to your blog from sites in foreign languages; it would be just as beneficial as an English link. Try to get relevant ones though.
How did your father manage to get a PR4 without link development? That is simply fantastic. You might as well get your dad to put you in blog roll, so that you get the benefits from his blog