I'm sorry, this is just insane then. Divorcing someone on the grounds that they had a child before you were ever together and didn't know about it? Sounds like bullshit. Sucks that this guy thinks he's responsible for breaking up his parents.
If you think that's bullshit, you're not considering all the possible factor, or don't understand how a decades-old marriage works: through lots of compromises, that people sometimes feel unhappy about, but not enough to risk what they've gotten used to.
So maybe the mother had felt (probably for years) that the father wasn't appreciating her enough. And now he's making more effort to connect with this unknown child than he's spent on his wife and other children in years... suddenly the pent-up dissatisfaction comes out into the open, grievances are aired and people say hurtful things that make reconciliation impossible...
It doesn't actually make any implication that Tomas was conceived before they met. Maybe an affair early on in the relationship that the father managed to cover up.
>>Sucks that this guy thinks he's responsible for breaking up his parents.
In this situation I can imagine talking to my father about it, but talking to everyone else in a family was a decision he made. I'm not passing judgment either way, but he wasn't like he was passive here.
It's definitely not his fault, nor the fault of the test in question. No one should entertain a divorce based on circumstances from decades ago, and before you were even together. His parents aren't divorced because of the unknown son, nor his fathers natural inclination to contact him.