I believe John Marlow could of been in the 11th Light Dragoons which was the regiment name before?
Dragoons were cavalry regiments.
(From Wikipedia) Col. Phillip Honeywood's Regt. of Dragoons was formed 1715 at time of 1st Jacobite Rising. Retitled 11th Regt. of Dragoons 1751. Became 11th Regt. of Light Dragoons. Retitled 11th (Prince Albert's Own) Hussars in 1840. (Wedding present from Queen Victoria?)
According to another poster, John Marlow, Honora's husband, was a Royal Marines sergeant. IMO a Royal Marine was unlikely to have switched to a cavalry regiment, so probably a different John Marlow. Royal Marines were formed 1664 as Duke of York & Albany's Maritime Regiment of Foot. James, Duke of York, brother of King Charles, was Admiral of the Fleet. The regiment became known as the Admiral's Regiment. 1755 HM Marine Forces was formed under Admiralty control. It comprised of 3 Divisions, HQs at Portsmouth, Chatham and Plymouth. During the Napoleonic Wars the Royal Marines took part in every notable naval battle and in amphibious actions. In naval battles/skirmishes, they manned guns and fought in boarding parties. They were responsible for security of ship's officers and maintaining discipline of crew. You can see them in action in "Hornblower" TV series, repeated on various channels.
See Wikipedia article
https://en.wikipedia.org/wiki/History_of_Royal_MarinesEdit. The page is there. I had to click on a couple of others to find it this time.
Without delving deeply, it seems from what you've found out so far, that the Marlow family was a military one for several generations. There were many barracks in County Cork. Islands in Cobh harbour, port of Cork, were garrisoned. One was a prison. Look up Spike Island. More than a few local girls would have married soldiers.
The web-page you found about regiments on Malta is very detailed. Interesting bits about casualties.