स यद्येकपुत्रः पुत्रोत्पत्तावस्य प्रयतेत ॥ कZ_०१.१७.४८ ॥
sa yady ekaputraḥ putrotpattāv asya prayateta
If he has only one son, he should strive for the begetting of additional sons.
Redundancy reduces the probability of succession failure due to death, incapacity, or unfitness of a lone heir.