Complex sentence: Mabel was a gentlewoman of Queen Mary's Privy Chamber, and in February, the same year of his marriage to Mabel, FitzGerald had helped suppress the rebellion of Sir Thomas Wyatt.
Split into simpler sentences: Mabel was a gentlewoman of Queen Mary's Privy Chamber. In February, the same year of his marriage to Mabel, FitzGerald had helped suppress the rebellion of Sir Thomas Wyatt.