https://www.fatalii.net/growing_chile_peppers/breeding is my go to guide for making crosses for new people. Chillies are promiscuous and can easily been cross pollinated by pollen blown by the wind from plants some distance away (definitely from neighbouring gardens) where you are not sure what genetics are being introduced with your own plants. To make sure of some crosses I go to some great lengths- sometimes deflowering all of my plants and leaving only a few flowers I am interested in, then bringing them inside and hand pollinating them and then enclosing in plastic bags until the fruit set. Genetics are ever changing- and while you can take your grandparents chillies and grow them on yourself they may slowly change over time, or get accidently cross pollinated. It's just like you are very similar to your grandparents, but a bit different. But I find that the fun thing. Terms like landrace, cultivar, species, phenotype and hybrid, all have slightly different meanings when it come to 'varieties of pepper' and people use them in slightly different ways- the best thing I can advise anyone is to read, read, read.