Nope ... 

They may share the same working place, owner, and some employees but they are two distinct companies hence them bost hosting different sites with neither claiming to be a subsidary of each other ...

Any relationship nintendo builds with third party developers is good.

They share the same studio and technology. Straight Right is a different label to differentiate their "core" efforts from the more family friendly stuff they make under the Tantalus name.

Their still different companies in the end ... 

BluePoint is in a league of it's own, but I can see why Nintendo could use a competent porting studio.

With so much shared between them though, (owner, studio, employees, tech) they're more like two halves of the same whole.

They certainly share a lot but the Straight Right trademark is still seperate from Tantalus Media in the end ...

True, as a matter of legal technicality, but they may as well be the same entity for the purposes of their porting work with Nintendo; if it's an M-rated game they port it under the Straight Right name, (Mass Effect 3, Deus Ex) if not, under the Tantalus name. (Twilight Princess HD)

I think they may do it to a few very popular games like Pikmin 3 but in  general I agree that Nintendo will be aiming to come in with a new fresh set of titles

I dunno if it's so much to bolster the library per se as it is that there's plenty of good games on the Wii U that were criminally overlooked because the system didn't sell well. 

Pikmin 3, Bayonetta 2, Donkey Kong Country: Tropical Freeze, Xenoblade X, etc. etc. that I think Nintendo would want to double dip on with the NX. 

Like 75-80% of Nintendo hardware owners this gen were 3DS-only (no Wii U) ... that's a lot of people that didn't get a chance to play these games.