Chasidim generally get married young, at age 17 or 18, and generally marry a spouse of the same age as themselves. So the Chosen and Kallah are both 17 or 18.
The Chasidish disparity in numbers between the number of available boys compared to girls is proportionally much smaller than that in the Litvish world. The small disparity that does exist among Chasidim is generally one of more boys than girls.
Which is why especially among the less intense Chasidim you’ll find a lot of Chasidish boys marrying non-Chasidish girls. One of the good things about this phenomenon is that it alleviates the shidduch crisis among both Chasidim and Litvaks. It’s like a double-headed victory.