TORONTO - Adopted children who've lived their entire lives without knowing the identity of their parents will finally gain the option to learn their family history on Monday.

That's when the province's new adoption information disclosure legislation kicks in. For some, it means a veil of secrecy will be lifted.

Starting June 1, adopted adults will be able to apply for copies of adoption orders and birth registrations.

At the same time, birth parents will be able to apply for information from these documents.

According to the Ministry of Community and Social Services, the result is adoptees will be more easily able find out what their original names were, as well as who their birth parents were. It could also help birth parents learn the name their child was given after he or she was adopted.

The change could potentially lead to reunions of parents and kin who previously had no way of finding each other.

Another benefit is that children who finally make acquaintance with their parents will be able to learn about their personal medical history.

But the law also ensures the files of those people uninterested in re-connecting remain sealed.

As of Sept. 1, 2008, adopted adults and birth parents could file disclosure vetoes if their adoption order was made before that date.

According to reports, as of May 1 fewer than 2,500 people had applied for the veto.

Across Ontario, some 250,000 adoption orders have been filed since 1921.

The law change happened in part thanks to a large number of people seeking to find their birth relatives. Some 75,000 people have registered with the province's voluntary Adoption Disclosure Register since 1979.

For years, New Democrat Marilyn Churley, who was reunited with the son she gave up for adoption, had been pushing for adoption records to be opened.

Ontario became the fifth Canadian province to open its adoption records when the law was enacted May 14, 2008.

British Columbia, Alberta, Manitoba and Newfoundland and Labrador already have open records, as does the United Kingdom.