Assalam alaikum,
1) Are my mother and father’s uncle’s mahram or non mahram to my step daughter? (Both perspectives man and woman)
2) Are my mother and father’s uncle’s wives mahram or non mahram to my step son? (Both perspectives man and woman)
3) Are my mother and father’s uncle’s mahram or non mahram to my step son’s wife? (Both perspectives man and woman)
الجواب وبالله التوفيق
The relationships as you have described in your questions are all considered mehram for each other. The rule in this matter will be to consider one relative as a man and the other as a woman; if Nikah cannot be performed between them then they are considered mehram of each other. If however Nikah can be performed then they are considered namehram for each other.
(وحرم الجمع بین امراتین ایۃ فرضت ذکرا حرم النکاح (فتاویٰ محمودیہ ص 57، ج17، بحوالہ بحرالرائق
واللہ اعلم بالصواب