This is a known practice in Nepal among different communities and ethnic groups. Gurungs do this. Mama ko chori are the first candidate they are supposed to ask for marriage. Similarly, thakuris also have this tradition very common. I am half thakuri and I know a lot of relatives in my family has similar kind of marriage. Tharus often marry their bhauju if anything happens to Dai. Although these things have been very common to our tradition and stuffs, but it should be stopped and highly discouraged.

In your case the best will be to talk to your parents and see their reaction and go ahead accordingly.