There's no need to take him solely on his measurables. You can justify taking him 10-20 solely on on-field performance. His measurables suggest he has a very high ceiling...perennial pro-bowl type in time. But I think he'd still be a first rounder if he ran and jumped in the middle of the CB pack. If he were there at #23, I'd have zero problem with Belichick drafting him.
As far as his brother is concerned, Vontae can only learn from Vernon's mistakes. The reports I've read regarding Vontae during Combine week was that he came off as very humble in interviews.
I've mentioned this before, but Belichick burned a supplemental pick on J'Juan Cherry, who might be the biggest turd that's been on the team in the last decade, but couldn't wait to sign and keep re-signing his brother Je'Rod, who was a solid citizen, team leader, and future coach. If people start judging us based on our sibling's behavior, I, for one, am in deep, deep trouble.