Fernand Martin had 1 son Maurice who also worked in the factory of his father.
It now appears that at the age of 30 in 1902 he was also busy “inventing” toys.
I have only been able to find 1 patented invention so far.
I have never seen this toy in real life and it probably never reached the production stage.
Still interesting to read the description and look at the image.

Here is a translation of the French patent:
This invention relates to an automatic movement toy system consisting of a small subject whose frame or skeleton is formed by a coil spring.
This subject moves perpendicularly on a vertical rod, passed through the hands of the figurine, as a result of vibrations that have been previously imparted to the spring constituting the body of the subject.
The invention in question will be well understood from the following description with reference to the attached specimen drawing, in which:
Fig. 1 represents the frame of the toy in question.
Fig. 2 shows the same subject seen from the outside.
In both figures, the same reference letters designate the same parts.
As can be seen in this drawing, the toy system in question comprises a body a “formed of a coil spring to which are attached the legs b, a head c and arms d“.
The arms are fixed on a small tube e into which a rod f is threaded.
To maneuver the small subject, it is sufficient to hold the rod vertically as indicated in the figures of the drawing, then to flex the body of the figurine representing a “clown” for example and the latter will descend along the rod by a swing of the body.
When the subject is at the bottom, the whole assembly is turned over, another descent occurs and so on.
The shapes, details, accessories, materials and dimensions of this toy system can of course vary without changing in any way the principle of the invention.
CLAIM:
An automatic movement toy system consisting of a small subject whose frame or skeleton is formed by a coil spring and which has in its hands a tubular piece in which a rod passes so that after having given the subject’s body an oscillating movement, it can move by a continuous swing caused by the bending of the coil spring forming the frame of the body, as described in principle and shown.

In 1907 Maurice became seriously ill probably struck by tuberculosis.
Maurice died of his illness on August 15, 1919 and Fernand Martin died almost 3 weeks later on September 4, 1919, aged 70 years.