Phew, I am certain I do not deserve those kind words, and nor am I sure that I can live up to them, but I will do my best to explain Kea.
The first thing to say is that not everyone who is K Negative, as your father must be, otherwise he would be unable to make anti-K (which is what they mean by saying he has made anti-Kell - VERY bad nomenclature on their behalf!). Except in certain, rare, pathological conditions, one does not produce an antibody against an antigen expressed on one's own red cells.
I suppose really, I should start by explaining some terms. An antigen (in this case, I am talking about something expressed on the red cells - they can also be expressed on white cells, platelets and other tissues within the body - but that will complicate things more than is required, so I will stick to red cells) is a structure on the surface of the red cell (usually either a protein or sugar) that, if these red cells are transfused to another individual who does not express the same antigen on his or her red cells, can stimulate the recipient's immune system to produce a specific antibody directed against this antigen. This antibody can lead to the destruction of the transfused red cells, should such antigen positive red cells be transfused to the same individual a second or subsequent time; so, in this case, if K Positive red cells are transfused to a K Negative individual, the recipient may produce an anti-K as a result, and if K Positive blood is transfused to this individual a second time (after a few weeks or months), those K Positive red cells may be destroyed in what is called a haemolytic transfusion reaction (please excuse my English spelling!). Another way in which such an antibody may be produced is if a woman is, for example, K Negative, and her baby is K Positive (the K gene would have to be inherited from the biological father for the baby/foetus to express the antigen on its red cells). Some antibodies are produced "naturally", without stimulation with red cells.
Two things are important to say here.
Firstly, an antibody is NOT produced by everyone when they are transfused with red cells that do express an antigen that the recipient does not express (or the pregnant woman does not possess -despite the fact that in almost all pregnancies there is a small bleed from the foetus into the maternal blood system).; the production of an antibody is by no means automatic.
Secondly, the transfusion of antigen positive blood to someone who has made such an antibody does NOT necessarily mean that they will have a haemolytic transfusion reaction (certainly not one that is clinically significant).
So, getting back to your family, your father MUST be (or have been) K Negative, and MUST have been transfused with K Positive blood at some point during his life (he, fairly obviously, could not have been pregnant with a K Positive foetus - and, if he was, I want to be his manager!!!!!!!!!!!).
Now, for an antigen to be expressed on an individual's red cells, they have to have inherited a gene, either from their mother or their father (or both) that encodes for that particular antigen (genes are inherited, but antigens cannot be inherited - they are the result of inherited genes).
Antibodies, on the other hand, which are found (normally) in the plasma (the "watery" part of the blood) once they have been stimulated CANNOT be as a result of inheritance (except very loosely, in that some, very rare individuals, never seem to produce antibodies, however many times their immune system is "challenged" by a "foreign antigen").
This means that, unless your elder sister is, as is likely, K Negative and then received either a K Positive transfusion, or was pregnant with a K Positive foetus, she is unlikely to have produced an anti-K. Similarly, if, as is likely, your brother is K Negative, he is most unlikely to have anti-K in his plasma, unless, at some point during his life, he was transfused with K Positive blood. The fact that antibodies are NOT inherited, it is highly UNLIKELY that your nieces and nephews will have anti-K in their circulation.
The McLeod phenotype is very, very unlikely, as is the McLeod Syndrome. They can both be inherited but would result in antibodies of different specificities than anti-K but may well also result in certain other pathological symptoms, so I really wouldn't worry about that.
Sorry, I have gone on a bit, and I hope this helps, but will attempt to attach a PowerPoint lecture that may explain things further, should you be so obsessed as to read it!
If this is not what you wanted, I would suggest you ask another member of this group, named "Danny", who knows more about the subject than I ever will.
In Depth Lecture on the Kell and Kx Blood Group Systems.pptx