100-brother(s) and sister(s)?

[matilda]

Hello every body

Which form is correct?
1-Sarah and Peter, who were brother and sister, ….
2-Sarah and Peter, who were brothers and sisters, ….

Thanks

Matilda

[HCaulfield]

It's one brother and one sister, so I'd go with 1.

Or Sarah and Peter, who were syblings, ...