Fought on the anti-royalist side in the Civil War. In 1652 he married for the second time to Bridget, Cromwell's daughter and widow of Henry Ireton. That same year he was appointed Lord Deputy of Ireland, 1652 - 55, where he ruthlessly imposed the terms of the Act of Settlement.
Bridget died in 1662 and Fleetwood married again in 1664 to Mary Hartopp, acquiring an estate with a house fronting onto what is today Stoke Newington Church Street. The house, built in the 1630s, an immediate neighbour to Abney House, became known as Fleetwood House and was demolished in 1872. London Gardens On-line has some good information about both these houses. Fleetwood was buried in Bunhill burial ground, in his third wife's tomb.
His children by his first wife were both married to the children of his third wife, Mary, by her first husband. More details on Mary's page, but hold on to your hat!