A Calgary father is pleading with the federal immigration minister to help him get past a frustrating rule change that he says is keeping him from his youngest son.

Andy Buck came to Calgary from the United Kingdom in 2008 after landing a job with the city. His sons, who were 14 and 17 at the time, stayed back with his ex-wife.

"It was an opportunity for me to better myself, but the by-product of all that was the fact it would create opportunities for my two boys also,” Buck told CTV Calgary.

Andy became a Canadian citizen three years ago and when his older son, Alex, turned 19, Buck sponsored him as a dependent child to come to Canada. Now 25, Alex works for an engineering firm in Calgary.

In January, 2015, Buck’s younger son, Benjamin, decided he wanted to join them too, but the family soon hit a roadblock.

They learned that the former Conservative government had adjusted the rules on sponsoring adult children in 2014, changing the age of dependency from children under the age of 22, to children under the age of 19.

Under those rules, only children 19 and older who were unable to support themselves because of a mental or physical condition could be considered dependents. Young adults not considered dependents would have to apply to come to Canada on their own merits, or as foreign students.

Ben, who had just turned 19, learned he was too old to qualify as a dependent.

"It is very frustrating. I just want to follow my dad's and brother's footsteps,” he said in a video call from the U.K.

But just last month, the Liberal government announced it would be changing the policy back, and returning the age of dependency to 22. It said in the announcement that the change was “consistent with the global socioeconomic trend for children to stay home longer” and would allow immigrant children to study in Canada.

But the rule change is not retroactive and doesn’t come into effect until October 24, 2017. Ben turns 22 in July so by the time the switch is in place, he will once again be too old.

Ben’s father says it was “totally devastating” to realize he won’t be able to bring his son over. Ben’s brother Alexis is also frustrated.

"To be denied on what was a slight rule change that is now getting changed back is totally unjust,” he says.

The Buck family is not alone.

'Lost children'

Raj Sharma, a Calgary immigration lawyer who is not representing the Bucks, says several families are finding they are caught in the gap between the old policy and the new. He calls all those affected "lost children."

"I think it is unfortunate and it's completely avoidable,” Sharma said. “And I think there are other families affected and they will come forward as well. The minister will have to deal with this today or tomorrow.”

Though Immigration Canada says it’s commited to family reunification, they say the reason the new policy isn't retroactive is because it will impact wait times for those already in the queue.

But Sharma wonders why exceptions can’t be made.

“If you were the one caught up in bureaucratic mess, there should be room for you to come,” he says.

Buck tried applying for Ben on compassionate grounds, but the application was denied. The family is now appealing to Immigration Minister Ahmed Hussen for help.

A representative for Hussen told CTV News he can’t comment on the case since the minister doesn't speak about specific cases.

With a report from CTV Calgary’s Kathy Le