Do mother and son mallard ducks mate when they are older or even young?

Hi everyone :) I was just wondering if a mallard mother duck and her son (baby or adult boy duck) would mate? And about how old would they be if they did? Because I have a mallard nest in my backyard (i live not too far from of a creek). I was very lucky now to be able to watch them hatch! (as i didnt get any closer than 8 feet or she might leave the nest) And she & her son and some of her other little ones come to my pool and food outside in a feeder. I have been watching them (never getting closer than 10 feet) and it almost seems her and her 1 son have been getting quite close. I was wondering if they are mating? Thank you for the help :)