They will grow straight if splinted in one of the ways described, providing they are not so badly splayed that the legs are stuck out at right angles to the body
It is not hereditory, but caused by a lack of the B vitamin Riboflavin in the diet of the breeding hen.
Many people who hatch eggs do not realise that, unless the hens are free range, they need a breeders' ration as a layers' ration only provides enough vitamins to produce an egg. For the egg to hatch into a healthy chick requires a better quality diet. Free range hens obtain the necessary nutrients from the grass etc. that they have access to.