There is 1 node with multiple wallets. Each family member uses the same node. I opened the "lightning terminal" then navigated to Connect => Lightning node connect, created a new connection choose "custodial account" and scanned the QR with ZEUS wallet.
the node, channels, liquidity is same for everybody.
How about channels?
Does each of your family members has separate channels connected to different lightning nodes?
Okay, so the statement in the OP now checks out; it's a "
custodial account" setup where your node is the custodian.
AFAIK, each custodial account should have a "
virtual balance" that's managed by your lightning node rather than actual channel capacity.
Unfortunately, now that it's clear, I came up with the same question why it was routed.
Is this consistent to other transactions between your custodial accounts?
If not, investigate the wallets where it occurred, both sender and receiver.