You can book tickets for another person from someone else's Skymiles account. If you're trying to book each ticket from a different SM account, you have to book them individually. You obviously won't be on the same PNR and if one person has lower or no status they won't get the benefits of the higher status person.
As an example, if you're a PM and the other person has no status they won't get a complimentary C+ upgrade.
You can book both tickets from one persons SM account and then you'd be on the same PNR and get your PM benefits.