Living with Grandma update

Last year my gran Pamela moved in with me after a fire in her apartment block. We got on very well together and after she caught masturbating in the bath, I asked her to take over the stroking and she did. We ended up in my bed fucking and have continued sleeping together and regularly fucking also. Then May this year Marilyn 23 my cousin came to the city for work and also see Pamela. Marilyn is quite shy and Pamela had asked her to stay with us, at first I thought it would stop the sex with Pamela. But as I work from home and when Marilyn was at work Pamela gets me to fuck her. Then at the end of June I had to go away for 5 days and on my getting back, Pamela got me to fuck her straight away. After I had fucked her she told me I should bed Marilyn, I told her I didn't Marilyn would let me. She said go out tomorrow night and let Marilyn think you won't be home till very late. Then return around 9 and you can catch us in bed together and join in fucking us both. I was a little confused and asked how do you know you and Marilyn will be in bed together then. Pamela told me she had seduced Marilyn while I was away and I can get her into bed anytime I want. Okay I said, so the next evening I said I had business to take care of and would be late returning and left at about 6 and went and seen a movie and after headed home, getting into my street about 10 to 9 I parked down the street from my house and waited a few minutes. Then drove into my carport with the headlights off. I was a silence as I could be and entered the house and nobody to be seen. I headed for Pamela's room and the wasn't fully closed and I could Pamela had Marilyn going down on her. I got an instant hard-on and so I enter and quickly undressed and was up behind Marilyn before she could recover from the shock of being caught licking Pamela's pussy and with Pamela telling me to fuck Marilyn I went for it and she didn't try and stop me. I shouldn't have left my sperm inside her, but it didn't dawn on me that Marilyn wasn't on any protection what so ever. Also I was her first male sex partner. After I had finished Marilyn, Pamela said my turn and went down on me to get me up again. Marilyn was still in the state of shock and just laid there, after I started fucking Pamela. Pamela told Marilyn to sit on her face and also kiss me while fucked Pamela. After fucking the two of them I was well and truly drained. Only after about hour had passed did Marilyn mention she wasn't on the protection of any type. Pamela said no worries we'll keep in the family. In late July Marilyn tested positive to being pregnant. Pamela got her tested for everything and the baby was shown to be very healthy. Marilyn's mother Katherine 42 war widow wasn't very happy her only child was pregnant to her sister's son. My mother Joanna 45 divorced was also shocked her only child had gotten her niece pregnant. But Pamela told them what is done is done and now we have to make the best of it. Katherine got a transfer and came to live with us and Pamela soon had her also joining in fun as she calls it. Last month Joanna also came to live with us and has also started enjoying the family fun. None of us are centerfold models just average. But we do really enjoy the sex.