Is it obligatory for one who feels something coming out of their anus, without sound or smell, to exert pressure on themselves so that their ablution is not invalidated during prayer?

If your brother can control the release of wind, he must suppress it during prayer unless he is harmed by doing so; otherwise, it is not obligatory for him. If the release of wind is constant for him, such that he cannot find a time for purification and prayer without it being released, then he is considered to have incontinence ( سلس ), and there is no need for him to perform ablution more than once. However, if the emission stops for a period that is sufficient for purification and prayer, then he is not considered to have incontinence, and his ablution is nullified by the release of wind, and he must suppress it if it does not cause harm. Doubts about the release of wind are not to be taken into consideration.