Is the repeated failure to conceive (for the brother and sister), and the repeated miscarriages (for the questioner), evidence of punishment or wrath from Allah, and what should she do for Allah to bless them with children?

Childbearing is a provision from Allah. A servant may be deprived of it due to a sin or as a trial from Allah. Abundance of provision is not always a sign of honor, nor is its scarcity always a sign of humiliation. Rather, Allah may bestow abundance upon a disbeliever and restrict it for a believer. One must trust in Allah, supplicate, exert effort, and be patient, for Allah will pay the patient their reward without reckoning.