Though you correctly give the census district as Onchan all addresses are in Old Douglas - Drumgold street was just off Duke street where the new M&S store is, Bigwell Street is now the continuation of Lord Street and is about 100 yards from Shaws Brow.

The name Lewis is remarkably common at that time - some 26 below age of 20 having it, with several L.H.'s thus it is likely that the 5 and 10 year old are different people