If Google thinks two sites have a relationship (i.e. have the same owner), will links between those two sites...
A.) Be devalued/discounted and not pass Toolbar pagerank or true pagerank.
B.) Be devalued/discounted and pass Toolbar pagerank, but not true pagerank. (to confuse link spammers)
C.) May or may not be devalued/discounted, and pass Toolbar and true pagerank based on the decision to devalued/discounted.
What I'm getting at is, if the same owner has two sites that link together, and there is a TBPR increase from those links, does that mean that Google either doesn't know, or doesn't care if the sites are owned by the same person.
If you have good and trusted sites - where is the problem? Google has a big network of sites and blogs. Most are linked each other. I think its absolutely OK to have more than one good site. Good luck :-)