'Twas Barristan he asked, not Renly, I believe. OT: Yes, it's indeed plausible that Russell Merryweather's Robert's secret bastard. As for others, it seems we haven't met anyone who could be one; All of Robert's confirmed and speculated bastards have the trademark Baratheon look, and they're about the only ones with that exact look.
Well, he seems to be a full-fledged coldhearted sociopath, so I can't say I like or admire him. But for the purpose of this thread: He certainly deserves recognition for having stayed on the Starks' good side up untill the Red Wedding. His rule of a a quiet people has allowed him to avoid any suspicion on what's been going on in his lands - if Ned knew of even half of the misdeeds Roose had done for his pleasure, he'd have gone to air Ice a little at the Dreadfort.