Is this normal for a mom to do?

Is this normal?

I have a daughter (age 4) my husband has a daughter (also age 4) and we have a newborn. I breastfeed my daughter until she was 3 months from turning 2. My husband’s daughter was formula fed until changing to cows milk. My husband’s daughter’s mother has an almost 1yr old as well. My husband was just told by her mother that she has started breastfeeding her because she likes it. Is this a normal thing? Or am I just being creeped out for nothing?

Just to make sure i understand it right… she’s started breastfeeding the 4 year old?? To me that’s weird, especially if she was bottle fed as a baby. She may have started breastfeeding the 1 year old & felt the connection it gives and wanted that with the older child or maybe she started doing it because you did it with your child with him but still…kinda weird.