Appreciate this may seem uncool but im only asking. Ive received an email saying i can gift Avios and if i do so they will get an extra 40%

So lets say i gift my sister 100k which means she gets 140k.

Can her partner then gift me 100k from his account giving me 140k even if he has a family account with my sister ?

And is it possible to gift to people at your same address as im looking at the rules and cant see any mention of not being able to do this between family members ?