Assalamu Alaikum Varahmathullah
At what age non-mahram family and nieghbour boys and girls to be splitted from playing together and talking together?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, sallallaahu 'alayhi wa sallam, is His slave and Messenger.

If the children are below the age of distinction – which is seven years – then there is no problem for the boys to play with the girls. The same thing applies to those who have reached the age of distinction, seven or so, there is no harm if they play together.

Nonetheless, some educators are of the view that it is better to prevent them from that [i.e. allowing boys and girls who have reached the age of distinction to play together], so that the males would not be influenced by the nature (or character) of females and vice-versa.

This is in addition to preventing anything that could spoil their morals or lead to the phenomenon of sexual harassment in the future. Undoubtedly, this varies from one environment to another.

When the girls reach nine or ten years of age, they should be forbidden from wearing clothes that do not cover their body decently, and from anything that can reveal parts of their body when playing in front of the males who have reached the age of distinction.

‘Aa’ishah, may Allah be pleased with her, said: “If a girl reaches nine years of age, then she is a woman.” [At-Tirmithi]

Allah has forbidden women from appearing [without Hijaab] in front of boys who can distinguish the looks of women (attractive or not); Allah Says (what means): {…or children who are not yet aware of the private aspects of women.} [Quran 24:31]

Ibn Katheer said: “Because they are so young they do not understand anything about women (their looks), their `Awrah, their soft voices or their enticing ways of walking and moving. If a child is young and does not understand such matters, then there is nothing wrong with him entering upon women. However, if he is an adolescent or approaching adolescence, and he knows and understands these things, and can distinguish between a woman who is beautiful and who is not, then he should not be allowed to enter upon women." [End of quote]

Imam Ahmad stated that girls who reach the age of ten years old should wear the Hijaab.

Ibn Qudaamah said: “Abu ‘Abdullah (i.e. Imam Ahmad) was asked: “When does a woman cover her head in front of a boy? He said: “If he reaches ten years old.” [End of quote]

Allah knows best.