Strategic love = tax avoidance.
No better or worse than friends Michael O'Sullivan and Matt Murphy.
A sister is sister. Not being a full-blood sister, or "half-"sister does not make her less of a sister.
In Ireland, "sibling" is a prohibited degree of kindship, and includes "half-" blood relations: consanguinity is consanguinity.
Incidentally, because of all the illegal adoptions in Ireland (thousands that will never be documented as they were not as sloppy as the few hundred the HSE has acknowledged), an inordinate of blood-relations end up as couples, after being attracted to one another by what they cannot explain, but that could be re-enforced by their unknown kinship.
This will always be a theory supported by nothing but anecdotal evidence, by definition, but it is one of the unintended effects of the perversions nd greed of the church leaders of the past century up to date.
As long as the OP and his sister do not pro-create (and I reckon it is not on the cards), then I could really not give a toss if they decide to get an incestious married and can benefit from a loophole to do it.
Typically dispensation would be provided in Sweden when the half-sibling were not raised together and preferably were not aware of their degree of kinship. But other things can be taken into account.
@Vikingraider28, was it a matter of recognizing an existing Swedish marriage, a matter of having a Swedish law marriage in Ireland but registered in Ireland due to medical reasons, or having an Irish Law marriage where the kindship prohibition got waved by an Irish or European court due to the fact that you could have married in Sweden if she had not been otherwise incapacitated?
Edit: in Ireland the minister can grant an exception for marriage of siblings by adoption.
I would definitely not support the idea that Ireland should celebrate all marriages that would be valid in other EU countries: after all Sweden has been struggling to deal with under-aged married migrants. That failure should not bind Ireland to recognize a migrant pedophile the protection of marriage.