... put a security lien on the property without my knowledge?

Hello c:

Do you mean can they obtain a mortgage or otherwise borrow against the property WITHOUT your approval??

The answer is NO.

IF that happened, your sibling is defrauding you. You can call the cops AND you can sue them. I don't know if I'd call the cops on my brother or sister... But, I'd sure as hell sue 'em.

excon

Define security lien? A sibling MIGHT be able to borrow against their share of the property without involving the other owners. More details will help us help you.