@Camilla ********
If he has a tourist visa he’d get 60 days on entry. If you are coming 30 days after him then if you come visa exempt you’d get 30 days. Now you’re “in sync”. After 60 days he needs an extension and so do you (or a bounce).
You are allowed 2 land border bounces in a calendar year. In theory there isn’t a limit by air but it’s up to the immigration officer to grant you entry. Successive back to back entries will raise red flags and possible questions or even denial of entry.