That's incest. It is illegal in this country be careful what you write here. You could end up in court
I always thought that incest had to be between a male and female so this made me think. I had a look at the Sexual Offences Act on line and it confirms that:
Incest relates to a male and female who are "closely related" so from a male viewpoint that would mean your Mother, Daughter, Granddaughter, Aunt or Sister.
So doing a Mother and Daughter isn't incest, there may be an element of sexual abuse if the women indulge in sex acts on each other but that's likely to be them getting prosecuted not you!! To be honest I think the old bill's primary interest (if there was any interest at all) would be TWO prostitutes working together from the same premises which makes it a BROTHEL.
I've seen a couple of Mother & Daughter ads on AW and also for sisters who work together most say something like "we do not do sex with each other only with the client"