The boys are very close in size so TBH they share more than hand them down. I've pretty much forgotten which undies belong to whom

I try to be an ethical consumer so even if I was inclined to spend money on 2 wardrobes I wouldn't because I think that sharing clothes in a family is the socailly and environmentally responsible thing to do.
This is the other thing too the girls CAN share clothes at the moment, including undies and it would make life so much easier to just throw all undies in 1 draw and then let them go from there until DD1 goes to the next size up....

I guess i just need to get over the 'don't share undies' thing and realise they are sisters, they don't have germs, they are clean, healthy little people there could be much worse than sharing undies.

Thanks everyone.