Shopping613: I quite frankly don’t believe you. At least not in the US. 13 & 15 are definitely not the norm to get married at in any Chasidish group here. If you’re discussing extreme cults like Helbrans (now in Guatemala) or maybe Yidden in Yemen (if there are any left there) that’s something else.
And many Chasidim have long engagements, so if someone is engaged at 17 (which is young even by Chasidic standards, but possible) it’s very likely he or she will be 18+ at the wedding.