DC1 will be getting a new bike for Christmas as his is too small now.
His old bike is still in good condition and perfect for DC2.
However DC2 would be fully aware that their sibling is getting a brand new bike while they get their old one. So more a hand me down than a gift. Also DC1 has asked for a new bike, DC2 has not (but desperately needs one as current one too small - but they love it.)
Last time they needed new we just gave DC2 the old bike (DC1 got current one for birthday).
On the other hand, it seems a bit unfair to DC1 that their Christmas present is "used up" by a bike, whereas DC2 just gets one "for free".
What's the fair way to handle this?