Does it invalidate his ghusl if some maniy comes out whilst he is doing ghusl?
Question

                If you realise a bit of sperm comes out whilst doing ghusl not after or before but during the process, is the ghusl you are undertaking invalid?.
Praise be to Allah.
    Emission of maniy whilst doing ghusl must be one of two 
    things: 

    -It happened with desire or

    -It happened without desire.

    If it happened with desire, then this invalidates the first 
    ghusl. So if he had washed his head and part of his body, then maniy was 
    emitted with desire, that invalidates his previous ghusl and he has to 
    repeat what he had already washed. 

    It says in al-Mawsoo‘ah al-Fiqhiyyah (5/220): The 
    fuqaha’ are unanimously agreed that emission of maniy is one of the things 
    that make ghusl obligatory. In fact, an-Nawawi narrated that there was 
    consensus on this point. 

    But if it happens without desire, and it is just the remnants 
    of the first emission, this invalidates wudoo’, but he does not have to 
    repeat what he has done of ghusl. See the answer to question no.
    49693. 

    Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said: 
    With regard to this questioner who emitted it, if there was no desire that 
    led to its emission, then it is the remnants of the first episode of 
    janaabah, and does not necessitate ghusl. All he has to do is wash it off 
    and wash everything it got onto, and repeat wudoo’ only.

    End quote from Fataawa Noor ‘ala’d-Darb 

    And Allah knows best.