my brother and his crazy girlfriend borrowed at least 20,000 and wont pay us back, should we sue?

brother and girlfriend were supposed to pay us back when the got there settlement but his girlfriend got her money and offered us zip nothing, now my brother getting his money and says he is not paying us back nothing, they even lived with us for over a year and were supposed to pay rent and they paid nothing..we aren't going to be able to have a christmas because we gave them are last 5000 dollars and we are broke so know i have o tell my son that there is no such thing as santa claus and its my daughters first christmas and we can't get her nothing.