Can I claim ownership of property I have been maintaining but not legally own?

Maintaining a property and paying its taxes, by itself, doesn't establish legal ownership if the formal title genuinely lies elsewhere — these actions can, however, be relevant supporting evidence if you're pursuing a claim based on long-standing possession, such as adverse possession, provided all the specific legal requirements for that claim (open, continuous, hostile possession for the statutory period) are actually met.

Your first step should be a thorough title investigation to actually understand who holds recorded ownership and the history of how the property came to be in this uncertain state — this will determine whether you're better placed pursuing a declaration of title, adverse possession, or negotiating directly with whoever the formal owner turns out to be.

Given how much depends on the specific facts and documentary history here, it would be important to consult a property lawyer to conduct this title investigation and advise on the strongest and most realistic path forward for your specific situation, rather than assuming any one particular remedy will necessarily apply.