Please advice me about Adultery and child custody and a potential kidnapping

Hi.. Please be patient and hear my case

My cousin and her husband isn't separated verbally or legally but her husband is working as a trainer in a call center company in laguna and my cousin a housewife in QC. my depressed cousin taking the weight for 4 yrs. hoping for her husband to live with them... they talked trough phone only but it seems nothing wrong or anything but when she received a call from the 1st mistress with confession, their baby and told her about his husband's 2nd mistress' relationship started in september 2017 for her to be agitated and try to do something to the 2nd mistress...

just this year she allowed her eldest son(13yo) to study in Laguna hoping that this connection would allow her and her daugther(10yo) to move to her husband's place.

What happened is that the 2nd mistress took interest of her eldest son and want to take him with them when they moved to their province somewhere. The husband and the 2nd mistress spoke to her and inform her that they are going to take her eldest son and of course she replied NO.. still shocked she looked for things she could do to at least get some support from her husband's family and to her dismay they already know about this and her mother in law even formulated a plan to allow them by stating some law. they said that the eldest sont(13yo) has the right to choose who to live with(probably brainwashed already). To her surprise a post seemingly her husband, 2nd mistress and her eldest son are all now in cotabato and was confirmed by the husband's family. all of this happened in less than 2 weeks.

so my questions are:
1. this is Adultery right?(surely) what shall be our first action?
2. is there a way for her to get her eldest son back
   based from this Sy vs Ca G.R. 124518 she is the innocent
   party but she is currently incapable of supporting her 2
   children being a housewifre for more than 10 yrs.(based from my
   previous research)
3. Could this be kidnapping because she didn't give her consent to
   take her son away from her.
4. again from Sy vs Ca G.R. 124518 could the word "Moral
   Depravity" be applicable to the husband to prevent her for the
   custody.
5. Can she get the custody of both child against their will, also
   asking for child support or alimoni.
6. Are there any legal actions we can take against her husband's
   family?

I'm sorry if this is too long but I don't know how to Shrink this in my current state of mind being all of this happened too fast.

1. if they are married this may even fall as concubinage. hire a lawyer and file the appropriate case.
2. if she wants sole custody of the child, she will need to file this thru court (again if they are married).3
3. Unless they are not married.
4. Awarding custody has a lot of factors to consider. The more you have in your favor, the better the chances.
5. Possible. Kindly note that there is no divorce in the Philippines so no such alimony can be requested. Maybe your thinking of support? The father will still have to support the kids even if they are not in his custody. and if married, also the mother.
6. If all they did was be aware that their son has a mistress, then no.