Committal of perjury???

[Mildred88]

So my partner has a son- 8 years old. He split from the mum 5 years ago.
when the son was 1 year old, my partner found out she had been cheating on him. Done a DNA and the son wasn’t actually his, yet she’s named him on. Birth certificate as the dad knowing he wasn’t. But he gets paid more than the bio dad.

today she’s decided to tell the son without my partner being present and said she’s answered all questions herself and the son seemed to take it well, she obviously lied and made herself look good,
my partner is now worried as she’s committed perjury and also she will try take the son away

It’s nothing to do with what I feel for her, it’s seeing my partners mental health deteriorating due to how she’s conducted herself for the past few years and how she’s still tried to control him. The issue is the birth certificate, her being able to remove my partner after he’s been on it for 8 years, because of her wrong doing. He’s worried he will lose the right to be his father (non bio) because sadly, if she doesn’t get her way, she likes to throw a spanner in the works. Hence telling the child, without informing my partner or him being present to answer questions and know how she’s answered them, so please if you have nothing helpful to say and cannot see it from a different point do no view then keep your judgemental comments to yourself!
im querying if she understands the perjury aspect of things would she still have to remove my partner if she wanted too or would that deter her from putting my partner through further misery. I’m sure if you had a partner standing by watching their mental health wouldn’t be pleasant

Also focusing on an old relationship isn’t easy when the children are with us every other day because she doesn’t want to leave them go a day without seeing her, so we have to do bag hand overs with her daily at our convenience.
hard to not focus on it when it runs my life and the children live in MY house half the time