‘The 36-year-old, along with his brothers Sam, 48, and Don, 42, own the Akashi restaurant chain’ (Sunday Times Lifestyle, 7 September 2008).
Make it owns, because along with is not a conjunction. What this means in terms of grammar is that the subject of the sentence is singular (the 36-year-old), not plural, and requires a following singular verb (owns, not own).
The expression along with ... Don, 42 has no bearing on the grammar of the sentence. Indeed, we may move it around, or remove it altogether:
i. Along with his brothers Sam, 48, and Don, 42, the 36-year-old owns the Akashi restaurant chain.
ii. The 36-year-old owns the Akashi restaurant chain, along with his brothers Sam, 48, and Don, 42.
iii. The 36-year-old owns the Akashi restaurant chain.
Similar expressions include those beginning in including, together with, as well as and plus.
Incidentally, this is a favourite PSLE (Primary Six Leaving Examination, Singapore) question ... but it seems to be a little beyond the competence of our ST editors, some of whom are native speakers of English from countries such as New Zealand and the United States.