Charles Ellicott Commentary Luke 2:44

"but supposing him to be in the company, they went a day`s journey; and they sought for him among their kinsfolk and acquaintance:" — Luke 2:44 (ASV)

Supposing him to have been in the company.—The company was probably a large one, consisting of those who had come up to keep the Passover from Nazareth and the neighbouring villages. It is not certain, but in the nature of things it is sufficiently probable, that the boys of such a company congregated together, and travelled apart from the others.