Source: Fatāwā ʿUlamāʾ Ahl al-Ḥadīth, Kitāb al-Ṣalāh, Vol. 1, p. 243
Clarified for Sectarian and Social Guidance
Are such individuals considered Muslims, and is it appropriate to form marital or social relations with them?
✔ As long as these individuals adhere to the core tenets of Islam, they are to be considered Muslim, and praying behind them is valid.
This applies especially in situations of necessity or temporary leadership, where thorough investigation is not required.
✦ When appointing a permanent imam, however, preference should be given to someone with righteous conduct and sound beliefs.
✔ Similarly, there is no prohibition in establishing marital or social ties with Deobandi or Barelvi individuals, provided they maintain their Islamic identity.
In cases where someone has deviated from the truth, it is recommended to advise them wisely and compassionately, encouraging them toward correct Islamic teachings.
Reference:
Ahl Ḥadīth Suhādrah, Vol. 15, Issue 20
Clarified for Sectarian and Social Guidance
❖ Question
Is it valid to pray behind a Deobandi or Barelvi imam?Are such individuals considered Muslims, and is it appropriate to form marital or social relations with them?
❖ Answer
✔ Yes, Deobandi and Barelvi labels typically indicate affiliation with specific madrasahs or schools of thought, not a different religion.✔ As long as these individuals adhere to the core tenets of Islam, they are to be considered Muslim, and praying behind them is valid.
This applies especially in situations of necessity or temporary leadership, where thorough investigation is not required.
✦ When appointing a permanent imam, however, preference should be given to someone with righteous conduct and sound beliefs.
✔ Similarly, there is no prohibition in establishing marital or social ties with Deobandi or Barelvi individuals, provided they maintain their Islamic identity.

Reference:
Ahl Ḥadīth Suhādrah, Vol. 15, Issue 20