Ok. Thanks for the information. As you know, a court's paramount concern in child custody
cases is the best interest of the child
. A custody order is modifiable without proof of a substantial change in circumstances where such a modification is in the best interests of the child. McMillen v. McMillen, 602 A2d 845 (Pa. S.Ct 1992). Thus, your burden is only to show that it is in the best interest of the children to be placed with you. Given the time you have had the children, the fact that they have an established household environment and school environment, and given the actions of the mother over the years, it would seem that you have a very good position to claim custody.
As for the Gruber test, it has been incorporated into the ten factors enumerated in 23 Pa.C.S.A. § 5337(h), which provides:
In determining whether to grant a proposed relocation, the court shall consider the following factors, giving weighted consideration to those factors which affect the safety of the child:
(1) The nature, quality, extent of involvement and duration of the child's relationship with the party proposing to relocate and with the nonrelocating party, siblings and other significant persons in the child's life.
(2) The age, developmental stage, needs of the child and the likely impact the relocation will have on the child's physical, educational and emotional development, taking into consideration any special needs of the child.
(3) The feasibility of preserving the relationship between the nonrelocating party and the child through suitable custody arrangements, considering the logistics and financial circumstances of the parties.
(4) The child's preference, taking into consideration the age and maturity of the child.
(5) Whether there is an established pattern of conduct of either party to promote or thwart the relationship of the child and the other party.
(6) Whether the relocation will enhance the general quality of life for the party seeking the relocation, including, but not limited to, financial or emotional benefit or educational opportunity.
(7) Whether the relocation will enhance the general quality of life for the child, including, but not limited to, financial or emotional benefit or educational opportunity.
(8) The reasons and motivation of each party for seeking or opposing the relocation.
(9) The present and past abuse committed by a party or member of the party's household and whether
there is a continued risk of harm to the child or an abused party.
(10) Any other factor affecting the best interest of the child.
You can certainly use these factors to claim that you should be granted custody as well.
As for the siblings, the judge can consider that when determining custody, but it only has a real impact if they have an established relationship, which it sounds that they are not. Also, the fact that they are half-siblings should minimize the relevance of there being siblings.
I hope this answers your questions, but if you have others, please REPLY and I'll be glad to respond. Thanks.