Relationship question

This is for my little sister but she did ask the question by herself. She met a man who is complaining all the time that he doesn’t want to be in relationships with the woman he is living with. And apparently making subtle moves towards my sister. So she is asking if he dumps her current lady and will date her instead. (Or is it just big talk without real intention.) I actually don’t know who is who here. I think 1st and 7th are my sister and this man. There is applying trine between them. But is it too wide. Is the Saturn his current lady then?

If she asked the question then the ascendent is your sister. She's in her own house but in detriment (the sign opposite the one she rules), so weak, but coming to a trine with romantic illusionary Neptune in her 5th of love affairs. The moon is approaching a sextile with mars, who is in his own 12th of limitations and frustration, and near Chiron of pain, weak in pisces. So it would seem he is in a weak position but he is sincere about it.

Your answers are always insightful and informative Is there any action ahead? If that are both weak to take actions maybe it’s better just wait and see? Neptune is her 7th house ruler in natal chart. Is it relevant?

If we just read this sentence, "a man who is complaining all the time that he doesn’t want to be in relationships with the woman he is living with", we should ask ourselves, without a horoscope, So why hasn't he simply left the woman he is not happy with instead of complaining to others about it?". Does his current partner think he is happy with her, has she any idea he wants out? If your sister enters a relationship with him, where he casually slip slides from the old to the new (she being the new), would he then treat her in the future in the same way?
His qualities, mars in pisces in his 12th, don't promise very much of a character as a man.
You say your sister's 7th is ruled by Neptune, so maybe this is the type of man and relationship she dreams about. But there are many ways it can manifest itself (pairing off with a poet or a musician or a religious man, for example).
They say, be careful about what you wish for, you may get it.
Your sister isn't in a strong position right now, approaching illusive Neptune, and also she is opposite the part of fortune, so her judgement is off.
She has nothing to lose by waiting it out, to see how he acts with his current partner, and decide from there.

Don´t let your sister near that person. She will only absorb a man who is dealing with a problem and later she will become a problem herself.
It´s a cycle , people who are in the middle of a "baggage", if they do not solve it ,they will attract more problems by trying to ignore the other one and they pile up.
This is so typical , people meet and they only see Kings and Queens until all the trash they carry gets thrown to eachother and the passion dies! Why? Because that´s law of attraction.

Sorry for the mood kill but it´s true. We cannot save other people , we can help them but getting saved is up to them.

Thank you both! They have known each other about 10 years. I have met him too several times. And I know she thinks he is a reliable man. And she told me that he and his current ladyfriend has discussed that their relationship will not last forever. (If true) And that he doesn’t want to have babies with her. (He want to have more kids with someone.) Apparently he entered into that relationship after a divorce. He has one child that is living with him every other week and he has to think stability of that child’s live too. It seems complicated situation.

What he says he discussed with his current partner and what he really did discuss with her are not necessarily the same thing. Let him first solve the situation with his current one, like bakalhau69 says. Once he has his own life, and supporting the child he already has, then your sister might consider being with him, if she still thinks he's good partner material. The fact that a man is divorced with a child, and had a second failed relationship does not necessarily mean he should be discarded, but first he should work out his conflicts and set his life straight.
On the other hand, when bakalhau69 writes "Don´t let your sister near that person.", I don't agree, only because every person has to work out their own destiny, and you can't close your sister up in a closet and make choices for her. She has to understand for herself what the situation is, and make her own choice. She has to work out her own internal conflicts and learn to act for her own good, and the good of others. You can't impose this on her. Remember the old saying, still very valid, "you can lead a horse to water, but you can't make him drink!".
Good luck, keep us posted as to how it turns out.