The question was: Is someone michuyiv to pay Shadchanus to a family member? You don’t write the family relationship. If the boy or girl’s father or mather is the shaddchan, then there is no chiyuv for shadchonus because chazal tell us that there is a chiyuv on the father “l’ha’si’o isha” (to mary off his son). (I assume the same applies to a mother – that she has a chiyuv to marry off her son, and I assume this chiyuv on the parents also apply to a daughter).
In other words, you don’t need to pay someone for doing their mitzvah, even if you benefit from it. (Just as you don’t pay the Kohen for duchan – giving you brochos, since that is his chiyuv).
Bays and Girls, That is today’s lesson. Be bsimcha with mishteh yayin – tomid (that is a chiyuv and halacha – for those who keep halacha).