I'm guessing you are referring to couple at Smelt house Derbyhaven - his probable widow is it appears still in Derbyhaven but on parish relief in 1851 so may be no money for a MI - many MI's from this period

how do you know he was born Malew in 1781 ? - there is an 80yr old robt bur 1848 Malew - he could be older or not born Malew - eg Robt Kelly + Cath Corris mar in Braddan had children in malew and might well fit this couple with the 15yr old John a grandchild