Inviting half siblings to your wedding
I am 29 years old and will be getting married soon. I have two teenage half-siblings ages 14 and 15 (we share the same father). My dad and stepmother were married for 17 years (actually still technically married) but have been separated for the last four years. The kids live with their mother (my stepmother). I have not seen my stepmother in the last five years and I have only seen my step-siblings just a few times in the last several years (the majority of the time of I was in the military, but I never wrote or contacted them the entire 4 years I was gone). Needless to say I am not close with my half-siblings or my former stepmother.
Should I invite my half-siblings to my wedding? And should I send the invitation directly to their home of give it to our father to give to them? Or just tell my dad in his invitation that the invite is for them too? Also, now my father wants to bring his new girlfriend, who my half-siblings (teenagers) don't like. Should I invite my dad's new girlfriend too who my dad has been dating for three years now or tell my dad to bring the kids instead of her as I know the kids won't want to attend if they have to go with dad and this gf? Or should I even invite the kids and their mother (my step-mother) since I have known her longer than even dad's new gf. My own mother passed away last year and my mother and my step-mother never got along well at all which is probably why I don't keep in touch with my stepmother or my half-siblings now too. What is the appropriate etiquette and should I expect them to come if I rarely even talk, see, or know my half-siblings? Who should be making the effort in this half-sibling relationship at this point?
What is the etiquette when it comes to inviting half-siblings of parents who are separated, but had a long term marriage, and are still not technically divorced?