am i right or wrong?

if one child in a property is at risk of supposed sexual abuse would any other children in that property be too? right or wrong? just wondering because ive just lost custody of my oldest son because he is supposidly at risk of sexual harm from my partner because there an allegation that was dropped many many years ago on his record and his daughter from previous relationship on a child protection for emotional and sexual harm which has been going on for years and social services were trying to use this as a reason my son better off with his dad ....who was abusive to him... (partner was given temporary custody of his daughter at one point so if she was at risk why did he get temp custody ....he is allowed contact with his daughter umsupervised) ....we also have a 4 month old together ... they dont have any concerns about our baby being here ...so like i say if one at risk of sexual harm would any others be regardless of it being dad or not