If a successful Gallipoli campaign helped the Russian Empire survive, would Alexei's early death lead to a sister inheriting or another male Romanov?
Short answerThe next eligible male Romanov would inherit if Alexei had no son; surviving into adulthood would likely bring strong pressure for an early dynastic marriage.
NotesThe scenario assumes a surviving Russian Empire after a successful Gallipoli campaign. Alexei's hemophilia raises the prospect of an early death and a disputed succession. The answer expects another eligible male Romanov to inherit rather than a change of law favoring one of his sisters. If Alexei lived long enough, an early dynastic marriage could be attempted in the hope of a son. The result depends on his age at death and whether that marriage produced a male heir.