So we needed to help each other, and in that sense the bond with my sister was strong.
Literal
Therefore mutually help-each-other need existed-because, that-kind-of meaning [in-で] [topic-は] younger-sister [with-と] bond [topic-は] was-strong.
Chains cause and conclusion: だから (therefore) plus ~ので (because) sets up why the bond was strong. そういう意味では (in that sense) is a common discourse framing phrase that narrows the scope of the claim. 絆 (bond/tie) became especially prominent after the 2011 earthquake as a symbol of human connection.