Found this video of someone trying to simulate two habitable planets with only the heat of each others tidal forces, and I would like to debate how life would live on a planet like that.
Obviously photosynthesis is not an option due to the fact there is no sun giving plants energy, but chemosynthesis or other things are possible. Animals would either have to think of a way to get bio-illuminescence (i hope i spelled that right) or not rely on sight at all. Tidal forces are obviously more impactful on the planet with the planets being so close together and all, probably effecting wave size quite a bit.
I will leave you guys to say other stuff about this