We know that Oliver Cromwell and Henry Ireton briefly considered putting him on the throne as a constitutional monarch, since, unlike Charles and James, he was too young to have the absolutist views of his parents. Then, according to their sister, Elizabeth, on their father's request, he refused to be crowned by the Parliamentarians so long as his brothers lived.
Then, he went with his famiyl to Paris, but became a staunch Protestant and often fought with his mother, so much so that he went to fight in the Spanish armies at Dunkirk, whe he gained his reputation as a great soldier.
IOTL, it was suggested before his death that he might marry a niece of Louis II, Prince de Conde. I personally prefer an alliance with Denmark and marriage to Princess Anna Sophia.