Who is Meng from A House Divided and what is their importance?

Meng is Yuan's youngest brother. He is a revolutionary, and over the course of time, we see Meng ask his brother to join the cause..... soemthing that Yuan refuses up until the point that his father demands he marry. In the end, after Yuan returns from America, he meets Meng again and realizes that Meng is no happier with leadership post revolution than he was before.