Generally speaking, the most important guest sits in the middle, number 1 is on their right side and number 2 on their left and so on.
In Western culture, partners are never seated next to each other during lunches or dinner parties.
Placing with one or several hosts
The host always gets the best seat and the most valued guests are seated next to them. In the event of several hosts, the guests and hosts are placed taking turns. For lunches and dinners, it is common to give each host their own table.
Source: Protocol to Manage Relationships Today (Amsterdam University Press, 2020)