The aim of this article is to analyse 20 Finnish working carers' perceptions of their sibling relations and the sharing of the responsibility for parental care. The main focus is on the interviewees' rationales for the participation or non-participation of their siblings in the parents' care. Almost all the interviewed carers stated that the division of care responsibilities is unequal and that they are the primary carers, but the majority did not convey any clear intention to try to persuade their siblings to increase their participation in parental care. In many cases, the siblings were described either as entirely absent or as providing occasional backup, but some interviewees reported that caring for the parent(s) was shared with their other siblings. Consequently, three participation patterns were identified: ‘absence’, ‘backup’ and ‘togetherness’. All the interviewees offered rationales for the unequal division of care tasks and responsibilities among the siblings. The discussion focuses on these rationales and their variations by participation patterns, and considers the similarity of the findings to those from previous American and British studies. The study concludes that social-care services should take the primary carer's siblings into consideration, although not always as a ‘resource’. It should not be taken for granted or assumed that the primary care-giver receives help from her or his siblings, even if their relationship is otherwise close and unproblematic.